The present invention relates in general to light metal wheel rims of the kind having at least two component parts such as that disclosed in German Patent No. 28 24 972 and U.S. Pat. No. 4,363,347. In particular, the present invention relates to wheel rims having internal and external rim flanges and adjacent corner regions for seating the internal and external beads of a corresponding tubeless tire.
The present invention also relates to wheel rims assembled from two or more component parts fastened together by bolts. In such wheel rims, a first component part includes the internal rim flange, a first curved portion for seating the internal bead of the tire, the rim ring and the wheel disk. The second component part typically includes the bowl shaped external rim bed and the external rim flange. In such wheel rims, the bowl-shaped rim beds are generally formed by forging, but they may also be formed by a press; the bowl-shaped rim beds are never cut. Heat hardenable aluminum milled alloys are typically used.
One feature which is often determinative of the shape of a light metal wheel rim are the diameters and spacing between the beads of the tubeless tire to be mounted on the rim. These dimensions are, of course, determined by tire manufacturers. The dimensions of the tire beads also affect the configuration of the internal and external rim flanges.
Within the rim, space must be provided to accommodate the brake mechanism of the vehicle. Minimum safety clearances must be provided between large diameter brake mechanisms and the wheel rim.
The internal and external rim beds cannot have any openings, other than for the opening passage for the air fill valve, as is possible, for example, in the case of wheel disks. This means that any opening passages can only be provided radially inward of the rim beds, through which opening passages heat generated by the brake mechanism can be removed. In this connection, those areas of the opening passages which lie at the greatest possible radius from the center of the wheel disk are the most valuable for the purpose of heat removal, since the centrifugal force (which acts to move air out through the wheel rim) increases with the square of the distance from opening passage to the center of the wheel disk. If, for example, 10 percent of the area of the opening passages are relocated radially outwardly, then heat removal is improved, not by 10 percent, but by approximately 20 percent.
Light metal wheel rims, particularly two-part light metal wheel rims are, however, not esteemed by the public solely because of their technical characteristics. Rather, their esthetic characteristics also play an extraordinarily important role. The more aesthetically pleasing a wheel rim is, the more it will be purchased by the buying public. For the technician shaping the form, there is available only the space within the radially innermost area of the outer rim bed, because this area alone is the visible area of the wheel disk. For this reason also, it is desirable to draw a visible area of the wheel disk as close as possible to the external side of the rim, and away from the vehicle. The technician shaping the form then has a correspondingly greater surface area available with which to work.
Damage to light metal wheel rims usually occurs in the area of the external rim bed, which is expensive to manufacture. Such damage occurs, for example, from roadside stones and other hazards. For this reason, it would be advantageous to be able to replace an external rim bed. The smaller the mass of the rim bed is, and the simpler its form, the more inexpensive the rim bed is, because large complicated forms are more expensive to forge than simple and small forms. The shorter the distance is between the radially outermost and radially innermost areas of the rim bed, the greater the rigidity the bed has for a given wall thickness. Therefore, a highly convoluted or very long rim bed is in this regard disadvantageous.
The task of the invention is to describe a construction which, with regard to the above conditions, permits an optimal construction. It should also be suitable to the various material requirements between the rim bed and the rim ring/wheel disk, which typically consist of different alloys. A tire should also be able to be mounted on such a wheel rim in a conventional manner and its construction should allow it to accommodate an air fill valve. Finally, of course, the condition must be fulfilled that air tightness of the tire internal space, relative to the environment, is maintained.